<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>省级城市</title>
    <style>
         a:link,a:visited{
                color: #222;text-decoration: none;}
           a:hover{color: #fd4913;}
    </style>
</head>
<body>
    <h2>省份城市的三级联动</h2>
    <select id="province">
        <option value="-1">请选择</option>
    </select>
    <select id="city"></select>
    <select id="country"></select>
    <script>
        var provinceArr=['上海','江苏','河北'];
        var cityArr=[
            ['上海市'],
            ['苏州市','南京市','扬州市'],
            ['石家庄','秦皇岛','张家口'],
        ];
        var countryArr=[
            [
                ['黄浦区','静安区','长宁区','浦东区'],
            ],[
                ['虎丘区','吴中区','相城区','姑苏区','吴江区'],
                ['玄武区','秦淮区','建邺区','鼓楼区','浦口区'],
                ['邗江区','广陵区','江都区'],
            ],[
                ['长安区','桥西区','新华区','井陉矿区'],
                ['海港区','山海关区','北戴河区','抚宁区'],
                ['桥东区','桥西区','宣化区','下花园区'],
            ],
        ];
        function createOption(obj,data){
            for(var i in data){
                var op=new Option(data[i],i);
                obj.options.add(op);
            }
        }
        var province=document.getElementById('province');
        createOption(province,provinceArr);
        var city=document.getElementById('city');
        province.onchange=function(){
            city.options.length=0;
            createOption(city,cityArr[province.value]);
        };
        var country=document.getElementById('country');
        city.onchange=function(){
            country.options.length=0;
            createOption(country,countryArr[province.value][city.value]);
        };
        province.onchange=function(){
            city.options.length=0;
            createOption(city,cityArr[province.value]);
            if(province.value>=0){
                city.onchange();
            }else{
                country.options.length=0;
            }
        };
    </script>
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